Some mods give you the tools you need to collect & process resources & get out of your way. Some mods add hot new toys to play with. Some mods, including IC2, make working your way up the tech tree the goal of the mod, which for me gets in the way of doing other things. I have had a dislike for IC2 ever since the 1st time I broke a machine that took over an hour to build because I forgot I had to use a special wrench to move it (blowing up a row of machines because I missed an upgrade in 1 while upgrading the power supply is also a big turn-off). When the Advanced Electric Jetpack & the mining laser were the hot new toys, I put up with it. With the mod that added the advanced jetpack MIA from the new mod packs & other mods offering a flight mechanic, I'm down to an extractor for rubber, a recycler (scrap boxes are like xmas!) & a power supply, & I cheated in the power supply. Every time I look at the new IC2 recipes I get the urge to cheat it in or do without.
If your goal is to create a massive pixel art statue in survival, you want a pen of sheep & an MFR rancher. If your goal is to create a large, complicated rube goldberg device to autofarm sheep, you can do that with vanilla mechanics. I play modded because I don't want to have to make a big project in order to gather the resources I need for another big project.